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Updated: Jan 20, 2021

A Cui-ui fish lays on its side. Find the original here.



Population Size: 1,000,000 adults (last record in 1992) ↑INCREASING↑


Brief Description

Swimming in a lake on the United States’ West Coast, the endangered sucker fish known as Cui-ui, Chasmistes cujus, is gradually increasing in population size. The Cui-ui, preferring wetlands, inhabits primarily the Pyramid Lake in Nevada and spawns, or lays their eggs, in the Truckee River; however, they once resided in the Winnemucca Lake before the lake dried up due to water diversion in the 1930’s. The Cui-ui often lives near shore areas within a small range of 150 feet (46 meters) in depth or less and will avoid steep slopes in the lakes. They have rough scales with a white underbelly and blackish-grayish coloring on their dorsal or top side. Adults can grow up to 27.5 inches (69.9 centimeters) long, and they can weigh from 3.5 to 7.7 pounds (1.6 to 3.5 kilograms). As a type of suckerfish, the Cui-ui use their fleshy lips to grab hold onto small rocks and suck any prey off like zooplankton, thread-like algae, and small aquatic insects.

In Pyramid Lake, extreme salinity, or concentration of salt, and acidity can prevent successful reproduction, thus they reproduce in the Truckee River for its water quality. Between 8- to 10-years-old, the Cui-ui will usually travel within 19 kilometers of the Truckee River between March and June to spawn or lay their eggs. To reach the spawning location, the Cui-ui need to circumvent multiple dams blocking habitable parts of the Truckee River. They will spawn in shallow areas of 8.3 to 55 inches (21 to 140 centimeters) on top of gravel without a nest and may spawn near the mouth of the river depending on the high flow rates. Once the eggs hatch after 1-2 weeks, the juvenile larvae will remain in their spawning location for days or even weeks before drifting back into the lake.

Currently, the Cui-ui face the possibility of extinction due to sand bars, industrial and agricultural use of the Truckee river, and their small habitat .

In 1907, an extreme drought created a sandbar delta that precluded the Cui-ui from travelling up the Truckee River except during wet years. Since then, sediment loading in the lake further reduces the quality of their habitat’s water due to siltation or the process of dirtying water with the suspension of fine particles. Moreover, industrial and urban expansion has decreased the water quality of the lakes through pollution as have agriculture through nutrient loads. Dams and construction projects mainly exacerbate and strain the Cui-ui in their attempt to spawn, but fortunately the Marble Bluff Fish Passage in the Marble Bluff Dam helps them pass through into the Truckee River. In addition, the Cui-ui fish are confined only to the Pyramid Lake which diminishes slowly because of water diversions and droughts. They cannot transfer or swim to any lakes with similar conditions to Pyramid Lake, increasing their vulnerability as a species.

Within 1982, the adult population only numbered at 100,000 as 92,000 originated from the single production of 1969. Although the spawning rate once was 13,000 in 1982, the spawning rate has dramatically increased to several hundreds of thousands by the early 2000’s with the last record of the adult population size at over one million. Because many scientists attribute the extremely wet years as a major factor for their population’s increase, the Cui-ui still retains the title of endangered as a series of wet years is an unreliable factor for a continual increase in population size.

Written by — Edward Keenan


Fun Facts

  1. Cui-ui is pronounced like “Kwee-Wee”

  2. They can live for more than 40 years

  3. The Paiute tribe reveres this fish and is currently helping to restore the fish so that the tribe may preserve their traditions

  4. The Cui-ui used to inhabit approximately 8,500 square miles (22,000 square kilometers) in Lake Lahontan, North America’s largest body of water 10,000 years ago

  5. They can travel at most to 40 kilometers into the Truckee River to spawn


How to Help

The U.S. Fish and Wildlife Service requires funding and volunteer efforts in order to send researchers out to evaluate similar bodies of water like Lake Pyramid and to record the most recent population changes of the Cui-ui. Donate or volunteer to help save this amazing species.

Through their efforts, workers at the fish hatchery and fish passage help preserve and cultivate Cui-ui fish. Take a tour or contact them to show your support.


Learn more!

Cui-ui Center for Biological Diversity

Cui-ui Redlist

Cui-ui (Chasmistes cujus) U.S. Nevada Fish &Wildlife Office

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